About 65 staff will be affected by the review of the office.
Representatives from the T&G, the GMB and Unison claim members are being ignored in the review.
They are taking their case to East Midlands Provincial Council of employers after Leicester refused to accept the legality of the grievance.
Union representatives say there is a threat of job losses, which is affecting morale while the review is taking place.
The council said it was not possible for a grievance to be lodged while the review procedure was under way.
'This is a fundamental review and under the council's procedures a grievance is not allowable. There are budget savings to be made and some major structural changes which some staff don't like. They are unhappy about the review but it is our view that it is being done according to procedure,' it said.
Redundancies will not be considered until the review is looked at by the council's policy and resources committee.